We’re finding out more about dinosaurs than ever – but their sex lives still elude us
Although they became extinct 66m years ago, dinosaurs are always news. The latest manifestation of that is the media shower generated by the discovery of the perfectly preserved leg, including remnants of skin, of a dinosaur in North Dakota.
It is suggested that this dinosaur, discovered at the Tanis fossil site, died on the very day the asteroid that caused the mass extinction of all the dinosaurs struck the Earth. It sounds almost too good to be true, but should make for a fascinating TV documentary next week, Dinosaurs: The Final Days, presented by Sir David Attenborough, naturally.
There are probably more palaeontologists working on dinosaurs today than at any point in history, and we have perhaps learned more about these incredible ancient reptiles in the past 20 years than in the previous 200. Plenty of once controversial and speculative ideas have been confirmed by the discovery of important fossils and diligent research on them. Dinosaurs were warm, active animals; some were intelligent and lived in groups; and they gave rise to birds, which are living dinosaurs.
These ideas have echoed in research for decades and have been mainstream from the 1990s onwards, but they act as a starting point for what has come since. We now have hundreds of specimens of dinosaurs, representing dozens of species, that are preserved with fossilised feathers. Moreover, we can track the evolution of feathers and their change from simple filaments to flight-capable aerofoils.
We have also discovered microscopic structures called melanosomes that in part give feathers and skin their colours, and allow palaeontologists to begin to reconstruct the colours and patterns of these animals. That’s an
astounding change in our ability to produce information from the fossil record and opens up enormous future possibilities for research.
Reconstructing the colour of a single individual, however impressive and interesting, is only of limited scientific value. We might be able to tell that it had a pattern that would work as camouflage, for example, or instead had very bright patterns that were likely for display, but it can’t tell the whole story.
Males and females were likely to have had different colours in many species, and birds moult their feathers, so bright breeding colours might only be around for part of the year or white winter coats might appear in others. Juveniles might be different colours from adults, and there could be regional variations, or things might evolve and change over time. All of these are reasonable possibilities and are the kinds of things that scientists can now assess. There’s huge future potential for a massive expansion in our understanding of dinosaur colours and signals.
This can also be integrated with other finds. In 2016, a paper was published describing bizarre pairs of scrapes dug into the ground that were made by large, carnivorous (and at least possibly feathered) dinosaurs. They looked as if an animal had almost pawed at the ground and excavated a furrow with each foot, and there were lots of pairs. There was no indication that they might have been digging for food or water, and they didn’t look like any known nest and would hardly work well as one. What they do resemble, though, are scrapes left in the ground by several different groups of modern seabirds during courtship rituals. This was, in fact, evidence of dinosaur displays and courtship.
It’s a fascinating find and some great deductive work went into eliminating the possible explanations to leave this as the most likely one. However, while it provides extraordinary information about how at least one dinosaur was trying to find a mate, it leaves far more questions unanswered. Telling dinosaurs apart from their tracks is not easy, and “large carnivorous dinosaur” is about as close as it gets.
It would be wonderful to say it was a tyrannosaur, where we have some ideas about their social interactions (they fought each other, a lot), but we don’t actually know, and it is all but impossible to find out. We also don’t know what else they might have been doing in addition to making the scrapes. There would very likely have been various other rituals going on, bobbing or bowing like geese and albatrosses, for example, calls between couples, all kinds of possible dances or other moves, and feathers (if present) could have been fluffed up and shaken. Did this go on for minutes or days?
We not only don’t know, but it’s almost impossible to conceive how we could know.
Thus, there are two distinctive and well-separated gaps in our knowledge of dinosaurs – the ones we are likely to fill and those that are almost impossible. The latter are numerous, but that doesn’t mean they are necessarily out of reach. Until only a few years ago I would have said that dinosaur colours were not only not known, but something we could never know, and that was true right up to the point that it wasn’t. When some enterprising researchers realised that melanosome shape was linked to colour and that melanosomes could be preserved, it opened up a whole new set of possibilities that we have only just begun to explore, and other “impossibilities” may one day fall. And, of course, the more conventional gaps will still be filled in. Palaeontologists continue to find fossils of new species, from new areas, and to be able to piece back together the evolutionary history of these most incredible reptiles though all the new data that is coming in.
So for all the frustrating missing pieces that we have in the puzzle of dinosaur biology across the nearly 200m years that they were around, we have more than enough pieces to see what the true picture is, and more and more gaps are being filled. There are plenty that we’ll probably never find, but it won’t stop our knowledge from growing or our understanding improving, and the future of dinosaurs is a most rosy one.
Dr Dave Hone is a senior lecturer at Queen Mary University of London, specialising in dinosaurs and pterosaurs. He blogs at Archosaur Musings, and presents the Terrible Lizards podcast. His latest book is The Future of Dinosaurs